Flywheel magneto assembly for in



Dec. 31, 1940. E B. Re. 21,679

FLYWHEEL MAGNETO ASSEMBLY FOR INTERNAL COMBUSTION ENGINES Original Filed Sept. 16, 1936 2 Sheets-Sheet 1 E. N. JACOBI Dec. 31, 1940.

FLYWHEEL MAGNET!) ASSEMBLY FOR INTERNAL COMBUSTION ENGINE S- 2 Sheets-Sheet 2 Original Filed Sept. 16. 1936 Pom 1's OPEN 1 imam Edward N: 19002 1 Reic'sued Dec. 31, 1940 PATENT OFFICE FLYWHEEL MAGNETO I TERNAL COMBUSTION Jacobi, Milwaukee, Wis., assignor to Edward N.

Briggs & Stratton' C ASSEMBLY roa 1N- enemas orporation, Milwaukee,

Wis, a corporation of Delaware Origin 1 No. 2,157,666, dated May 9, 1939, Serial No. 101,125, September 18, 1936. Application tor reissue June 27, 1940, Serial 9 Claims. (01. 123- 149) This invention relates to improvements in into the magneto assemblies therefor. It is an object of this invention to provide an improved magneto of the flywheel type whereby the size of the flywheel carried ring magnet may be proportioned to the magnetic requirements 1 -lthout regard for other factors.

it is another object of this invention to provide a magneto assembly of the flywheel type in which the coil and its armature core are mounted wholly outside the flywheel.

Another object of this invention is to provide a magneto assembly of the character described in which the coil and its core are so located as to be cooled by the air flow induced by the flywheel impeller so that efficient heat disipation is obtained with a minimum use of copper and iron.

In this respect it is a further object of this invention to provide a magneto assembly of the character described in which the coil is in the path oi air flowing from the flywheel impeller and is located so as to direct the cooling air to predetermined engine parts.

It is also an object of this invention to provide a magneto assembly which so disposes its ignition coil that the lead to the spark plug is exceptionally short.

Another object of this invention is to provide a magneto assembly wherein a quick reversal is obtained in the direction of flux flowing through the armature core upon which the coil is mounted.

More specifically, it is an object of this invention to provide a magneto assembly wherein a three legged armature core is employed whose dimensions are such with respect to the poles of the ring magnet as to insure a very rapid change in the direction of flux flowing in the center leg upon which the coil is mounted.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate a complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure l is a side view of an internal combustion engine with parts broken away and in section showing this invention;

Figure 2 is an end view of the engine with parts broken away and. in section; and 5 Figures 3 and4 are detail views showing the manner in which the direction of flux is abruptly changed.

Referring now particularly to the accompanying drawings, in which like numerals indicate like parts throughout the several views, the numeral 5 designates the crank case of a small portable combustion engine upon which a cylinder 6 is mounted. Ordinarily, the cylinder and the 'crank case are cast in one unit. The top of the cylinder is closed by a cylinder head I in which a spark plug 8 is secured. One end of the crank case is closed by a plate 9 and its opposite end is closed by a mounting plate It). The plates 9 and Ill have crankshaft bearings II and I2, respectively, in which the crank shaft l3 oi the engine is journalled.

Outwardiy of the mounting plate Ill the crank shaft mounts a flywheel ll, on the outer face of which is an air impeller IE to induce a flow of cooling 'air as hereinafter more fully described. Imbedded in the flywheel is a permanent ring magnet l6 having pole pieces l1 and I8 spaced apart a short distance andexposed at the outer periphery of the wheel.

The lower portion of the mounting plate is circular and substantially co-extenslve in size with the flywheel. Its upper portion is extended tangentially to provide an extension ill alongside the cylinder 6 and reaching up to the head 1.

The mounting plate with its 'upward extension '19 forms the inner wall of a blower housing and air guide 20, the other walls of which are formed by a stamped metal hood 2| which has a flat outer wall 22 of a size and shape roughly coextensive with that of the mounting plate and integral side walls 23 which extend inwardly to engage the peripheral edge of the mounting plate at all portions except one upper corner. This corner of the plate is cut away as at 24 to define an outlet'for the cooling air induced to flow through the housing by the impeller IS. The opening 24 is so located that the air issuing therefrom impinges the cylinder 6.

4 An inlet opening 25 to the blower housing and air guide 20 is formed in the outer wall 2! cpposite the center of the air impeller l5. Consequently, air is drawn in through the opening 25 and blown out through the opening.

- In the space within the housing 20 above the u mounting ID The coil is slipped onto retaining member 32'. In-

'airstream 2 V flywheelandalongsidetbeoutletopeningilso mounted by posts II on the outer face 01 the Plate extension I! in a position with the lower curved end races of its three legs 2!, 2O andillyinginanarcconcentrictoandslightlyspacedfromtheouterperipheryoitheflywheel. th pole pieces i1 and it successively sweep past the legs 28, I9 and ill to induce a magnetic flux whlch'is abruptly and rapidly reversed in direction, through the center leg II.

Mounted on the center leg is a conventional induction coil I! having a primary and secondary. the center leg 28 where it is held by a spring asmuchasthethreelegsot thecoreare parallel and lie sufliciently close together so as to obviate the necessity for inwardly projecting horns on the outer legs ll and 3., assembly 01' the coil core onto the core is a simple matter as it slides Ireely onto and oil oi the center 18:.

To obtain correct air gaps between the magnet poles II and "and the coil core poles 28, 29 and Ill, it is only 11 to slide the coil core downward against i'eeler gauges held between the coil core poles and flywheel periphery, and with the coil core held in this manner tighten its fastening screws.

One end oi the primary and secondary of the coil is grounded as at It. The other endoi the secondary is connected through the customary high tension lead with the spark plug; and the other end 01' the primary is.connected through a conductor 34 with an insulated terminal 3i 0! a circuit breaker. The other terminal or the circuit breaker is grounded and is also connected to a condenser ll in the customary manner. The circuit breaker is adapted to be actuated by a pusher pin 31, which'rldes on the crank shaft in line with a flattened portion 38 so thatthe pin is permitted to descend and allow closure of the circuit breaker once each revoluti It is tobeobservedthatallof the instrumentalities oi the magneto are mounted on the outer face of the mounting plate where they are readily accessible. especially the coil and its armature core. It is also be noted that this disposition of the coil and its core locates the same at a substantial elevation above the base where it is more likely to be clean and free from oil, and being mounted outside the flywheel and in position to be impinged by the cooling air, adequate heat dissipation is obtained with a minimum use of copper and iron. I

In this respect it is to be observed that the coil and its core are so mounted on the plate i9 as to lie alongside or adjacent to the side 01' the main issuing troin the blower and passing to the outlet opening 24. One side of the coil core thus forms a guide or wall extending along one sideoi themainairstrean'isoastobe cooled directly thereby. It is also to be observed that the curved bottom wall and tangential sidewall oi the blower housing. together with the coil deflnessuhstantiallyascrollcasingiorthecentrifugal blower impeller, and while the main air streamflows through this casing between the eoilcoreandadlacentsidewalloithehousingto lssuefrom the opening 24 and directly impinge dlrectpathotthecoolingtension lead to the any short.

' proportioned to the valveswhicharestthehottestportionot engine, other lesser air streams flow over thecoll and also past the other side of coil core to impinge the cylinder head.

Moreover. being mounted near the top of mounting plate near the cylinder head, the

one wall of the blower housing air guide, thus re- This permits smaller in diameter and in turn allows the engine to be built much lower than in past constructions, as the flywheel when the requirements of the length of the magnet bar needed for permanence is much smaller and much more economical of the m terial both in the magnet and in the flywheel proper than in a construction where the size of the flywheel is determined by mechanism which it must enclose.

Also, of particular importance is the fact that a three iegged'armature core is employed, for through its use a more eillcient magnetic machine is obtained. 7

As will be readily apparent particularly from Figures 3 and 4. the flux through the center leg 28 reverses abruptly and rapidly as the pole pieces I! and i8 sweep past the pole faces of the three legs. Being close together and mounted exteriorly of the flywheel adjacent to its periphery, the three legs of the armature core are swept by the magnet poles in a small annular movement to thus further assure rapidity in the change in direction oi the magnetic flux through the center leg 28 and consequently the coil.

In this respect, attention is directed to the fact that the arcuate length of the two magnet pole pieces i 1 and i8 is suflicient to span the distance between adjacent legs of the armature core and that the space between the pole pieces i1 and I 8 is less than or at least not greater than the arcuate length of the pole face of the center leg 28. This dimensional relationship is responsible for the exceptional rapidity! of the change in direction of flux for as will be readily apparent from Figures 3 and 4, the flux flowing in one direction (Figure 3) hangs on and continues to flow in this direction until the very instant that the flux begins to flow in the opposite direction (Figure 4). g I

From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art, that this invention provides an exceptiimally compact and magnetically efllcient magneto assembly for small portable internal combustion engines.

What I claim as my invention is:

1. In a magneto assembly for an internal combustion engine having a crankcase, a crankshaft and a cylinder mounted on the crankcase: a plate closing one side or the crankcase and having a part projecting alongside the cylinder; a bearing on the plate for the crankshaft; magneto parts carried by the plate adjacent to the bearing; a hollow flywheel mounted on the crankshaft and cooperating with the plate to enclose the magneto parts; a permanent magnet the magneto assembly also formsspark plug may be exceptioncarried by the flywheel and having poles facing the exterior of the flywheel rim; and anarmature coil core mounted on the side of the plate opposite .the cylinder so that the plate constitutes flywheel revolves.

2; A magneto assembly for an internal combustion engine having a crankcase with a crankshaft therein and a cylinder mounted on the crankcase: a flywheel on the crankshaft having its side which faces the crankcase hollowed to provide a cavity; a permanent magnet carried by the flywheel with its poles facing the exterior of the flywheel rim; magneto parts inside the flywheel cavity including a. circuit breaker for the magneto primary circuit; a cam rotatable with the crankshaft; a pusher pin operable by the cam to actuate the circuit breaker; an armature coil core having spaced limbs providing poles adapted to be swept by the poles of the permanent magnet; a plate closing the crankcase and the cavity formed by the hollow of the flywheel and having bores providing bearings for the crankshaft and the pusher pin and extending beyond the rim of the flywheel alongside the cylinder to provide a heat barrier between the cylinder and the armature coil core; and means for mounting the core on said extending portion of the plate.

3. In an internal combustion engine of the small portable type having a crankcase with a cylinder mounted thereon, a crankshaft and a flywheel fixed to the crankshaft: an air impeller rotating with the flywheel; a blower housing and air guide to direct the flow of air induced by the .impeller over the cylinder comprising, spaced walls between which the flywheel and air impeller are mounted, said spaced walls having a substantially circular lower portion with an upward extension disposed alongside the cylinder with the inside wall shaped to provide an outlet through which the air issues for passage over the cylinder, said walls being joined at their peripheral edges; a magneto for the engine comprising, a permanent magnet carried by the fivwheel with its poles facing the outer periphery of the wheel; an armature core having its poles lying. in an arc concentric to the outer periphery of the wheel so as to be swept by the poles of the flywheel carried magnet; an induction coil on the armature core; and means mounting the armature core on the extension of. one of said spaced walls of the blower housing and air guide so that said armature core and its coil lie in the path of the cooling air-flow induced by the impeller.

, 4. In an internal combustion. engine of the small po able type having a crankcase with a cylinder mounted thereon, a crankshaft and a flywheel fixed to the crankshaft: an air impeller rotating with the flywheel; a blower housing and air guideto direct the flow of air induced by the impeller over the cylinder; a magneto for the engine including an armature core and a coil on the armature core; and means mounting the armature core from one of the inside walls of the blower housing and air guide in such a position as to be in the path of the cooling air flowing through the housing.

5. In an internal combustion engine of the small portable type having a crankcase with a cylinder mounted thereon and having a crankalongside the cylinder, said housing having I spaced inner and outer walls between which the flywheel and air impeller are disposed; means for securing the inner wall to the crankcase of the engine between the cylinder and flywheel rim,

said inner wall of the housing having an opening outwardly of the fLvwheel rim to provide an outlet through which air may flow to impinge the cylinder, the outer wall having an entrance opening opposite the center of the air impeller; .a

magneto assembly for the engine including an armature core and an induction coil mounted thereon; and means mounting said armature core in the space defined by the extension of the blower housing and air guide adjacent to the flywheel rim and said opening so that the armature core is located in the path of the air-flow inducedby the impeller.

6. In an internal combustion engine of the small portable type having a crankcase with a cylinder mounted thereon: a plate closing one end a of the crankcase and having a crankshaft bearing in which the crankshaft of the engine is journalled; a flywheel mounted on the crankshaft and overlying the outer face of the plate;

said plate having its part which closes the end of the crankcase substantially coextensive with the flywheel and having an extension projecting a substantial distance from said part alongside the cylinder; and a magneto assembly mounted plate so as to be readily accessible and comprising an armature core and an induction coil carried by the core.

'7. In an internal combustion engine having a entirely on the outer face of the extension of said u crankcase and a cylinder closed by a cylinder 40 head and having a crankshaft with a flywheelflxed thereto: an air impeller rotating with the fly-wheel; a blower housing and air guide enclosing the flywheel and air impeller and extending along the cylinder head; an ignition coil and core mounted in the blower housing between the fly- 'wheel and the cylinder head end of the blower housing; and said housing having a. discharge port alongside the coil core whereby the coil core serves to guide the air issuing from the impeller to the discharge port.

8. In an internal combustion engine having a crankcase with a cylinder mounted thereon and having a crankshaft with a flywheel fixed thereto: an air impeller rotating with the flywheel and adapted to project a current of air tangentially from the periphery of the impeller toward the cylinder; a blower housing and air guide enclosing the flywheel and air impeller and extending along the cylinder and having a dischargeport so located as to discharge air onto the hottest portions of the cylinder; an ignition coil mounted in the blower housing between the flywheel and the remote end of the blower housing and to one side of the tangential air stream flowing from the impeller to the said discharge port. I

9. In an internal combustion engine of the small portable type having a, crankcase and a cylinder mounted thereon: a plate closing one end of the crankcase and having a-portion extended to lie alongside the cylinder; a bearing carried by said plate in. which the crankshaft of the engine is journalled; a, flywheel mounted on the crankshaft overlying said plate; a permanent magnet carried by the flywheel with its poles 15 facing the outer periphery of the wheel; an armature core mounted on said extended portion of the plate with its pole faces concentric to the fly. wheel and spaced slightly from the outer periphery thereof so as to be swept by the poles of the flywheel carded magnet; an induction coil carried by the armature core; an air impeller rotating with the flywheel; and a hood surrounding the flywheel and the plate, said hood extending over the front and top 01' the induction coil and armature core in close proximity thereto to a point directly adjacent to the side 01 the cylinder head, whereby the hood, the coil and the plate deflne a e for directing the air flow induced by the impeller against the cylinder walls of the engine. V

EDWARD N. J ACOBI. 

